Effects of cold water swimming on blood rheological properties and composition of fatty acids in erythrocyte membranes of untrained older rats.

This is the first report on the effects of a single bout of swimming to exhaustion in cold water on rat erythrocyte deformability, aggregation and fatty acid composition in erythrocyte membranes. The results indicate that there was a significant decrease in body temperature of experimental rats swimming in water at 4 degrees C and 25 degrees C when compared to the control. Erythrocyte aggregation indices did not change after swimming in water at 4 degrees C whereas erythrocyte deformability increased at shear stress 1,13 [Pa] and 15,96 [Pa]. Physical effort performed in water at 4 degrees C when compared to the control group resulted in an increase in monounsaturated and polyunsaturated n-3 fatty acid content in erythrocyte membranes that influenced the increase in their fluidity and permeability even though that of polyunsaturated n-6 fatty acids decreased. Physical effort performed in 25 degrees C water resulted in an increase in saturated fatty acid content and a decrease in all polyunsaturated fatty acids and polyunsaturated n-6 fatty acids when compared to the control group. Swimming of untrained old rats in cold water affected rheological properties oferythrocytes in a negligible way while changes in the fatty acid composition of erythrocyte membranes were more pronounced.

The effects of exercise in water at 4°C and 25°C on the rheological properties of blood and the composition of fatty acids in the erythrocyte membranes of laboratory rats.

The aim of this study was to assess the influence of a single session of maximal exercise performed in water (4°C or 25°C) on blood rheological properties and the composition of fatty acids in the erythrocyte membranes of laboratory rats. This study will permit better understanding of the reactions occurring in the organism during rapid cooling in cold water, especially in regards to the hemorheological and biochemical parameters of blood. When compared to the control group, exercise performed in water at 4°C led to an increase in the elongation index (EI, from 0.30 Pa to 4.24 Pa) with no concurrent changes in erythrocyte aggregation, blood plasma viscosity, and fatty acid composition (saturated, unsaturated, saturated/unsaturated, monounsaturated, polyunsaturated polyunsaturated-n3, polyunsaturated-n6 fatty acids) of the erythrocyte membrane. In rats swimming in water at 25°C, we observed an increase in EI at shear stress from 0.30 Pa to 2.19 Pa, along with a decrease in the half-time of total aggregation when compared to the control group. These changes in erythrocyte rheological properties can be treated as a protective reaction to thermal stress resulting in their improved deformability.